As a satellite-mounted shaped beam antenna, a reflector antenna whose aperture shape, in which asperities are formed on a mirror surface, is a circular shape is generally used in order to make it possible to transmit and receive a beam according to a requested service area.
For recent satellite-mounted shaped beam antennas, there is an increasing demand for improvements in the gain, suppression of the isolation, etc. than ever before.
As a measure to meet this demand, for example, there can be provided a method of improving the degree of freedom for forming asperities on the mirror surface, and enlarging the circular aperture shape which the main reflector has.
However, because the size of an antenna which can be mounted in a satellite is limited from satellite mounting constraints due to the fairing of rockets, the degree of freedom of reflector shaping is limited.
Therefore, in order to make it possible to maximize the utilization of the aperture area under the satellite mounting constraints, it is effective to use a main reflector having a rectangular aperture shape in which the four corners of its circular aperture is enlarged as long as it can be mounted.
A main reflector having such a rectangular aperture shape is disclosed by, for example, the following nonpatent reference 1.